Exploring the preservation of alkaline-carbonatitic extrusive rocks in relation to continent formation

Linda Campbell, A Dyer, C Williams, R. LYTHGOE P.

    Research output: Contribution to journalComment/debatepeer-review

    Abstract

    Mineral reaction paths related to continental alkaline-carbonatiticextrusive rocks are examined in the context of a“zeolitic masquerade� hypothesis [1]. The hypothesis suggeststhat zeolitic alteration reactions are the first steps in a gradualstabilization of these bedded successions, as the highlyreactive volcanic deposits change from glasses via zeolites toauthigenic feldspars, clays and SiO2 phases. Reported reactionprogressions are suggestive of trends in which Si/Al increaseswith time as wider, Si-saturated fluids react with earlier formedphases in continental environments. It is not knownhow trace elements such as the REE and HFSE behave at eachstage of reactive progression as no systematic study of theseelements has been made for wide occurrences of naturalzeolites. But our preliminary data indicate that the first formed,low-Si zeolites (e.g. phillipsite), reflect the REEpatterns of the original volcanic glasses. Modifications to traceelement signatures of altered successions are very likely tooccur as reactions progress with exposure to wider crustalfluids. Some of these modifications will be dependent on theion-selectivity properties of different zeolite minerals in thereaction paths, but fluid controls are certainly evident. Apreliminary exploration of possible examples in the geologicalrecord, of recognition and stabilization of reactive successions,is discussed.[1] Campbell et al (2012) Mineralium Deposita, 47, 371–382.
    Original languageEnglish
    Pages (from-to)814-814
    JournalMineralogical Magazine
    Volume77
    Issue number5
    Publication statusPublished - 2013

    Keywords

    • REE
    • zeolite mineralogy
    • reaction paths
    • alkaline pyroclastic rocks

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